Avik Bhattacharya
Ixia Product Development Manager

A Bike, a Few Clocks, and SDWAN

January 12, 2017 by Avik Bhattacharya

0As a kid, my school was a 10-minute bike ride away. But riding fast was a matter of pride amongst my friends, and I was able to get there within 3 minutes—or so I thought...

No – I wasn’t 330% faster than a rational rider.  I would only realize the reality later when one day I measured time using a watch and found that my travel time was about 8 minutes! Why was my time so much faster when measured using my home clock as the start time and the school clock as the finish time?

The Real Story of this Blog—SDWAN

Software-defined WAN (SDWAN) has been one of the most discussed SDN applications of 2016. The existing WANs were designed using dedicated MPLS links. Evolution of SDN provides programmability to the WAN, but the biggest business rational to introduce SDWAN is to make use of Internet bandwidth in place of dedicated MPLS links to bring down cost. Internet bandwidth cost is only 2% of traditional MPLS bandwidth cost. This gives birth to a concept of Hybrid WAN, which integrates dedicated MPLS, broadband, and 4G into corporate networks.

In a hybrid network infrastructure, an SDWAN solution needs to dynamically steer application traffic over MPLS or Internet links—on a per‐packet basis, to ensure enterprise-grade performance and availability. SDWAN gateways need to perform application-aware forwarding of traffic at line rate based on the policy inserted by the WAN Controller.


Compromising Performance for Cost?

An SDWAN solution transports data traffic through an overlay network on top of the hybrid infrastructure of existing MPLS or broadband or 4G-based Internet. Overlay processing, public network, and compatibility with existing network contribute to the overall latency of the system.

Every enterprise evaluating SDWAN will have one question in mind— Are they compromising performance by moving from a private MPLS circuit to a public Internet?

Therefore, it is of utmost importance for an SDWAN vendor to accurately measure the traffic characteristics in real-life high-scale environments.

SDWAN Validation Needs Timing  

Ixia’s IxNetwork is the most popular solution in the networking industry for measuring QoS characteristics of WAN traffic at line rate. It can generate multiple application traffic of different packet sizes and rates to stress the gateway. At the receiving side, IxNetwork can provide accurate measurement of latency of the WAN traffic. Accurate latency measurement needs an accurate and synchronized clock.


But the Home Clock – School Clock Problem…

By now it is obvious that my home clock and my school clock were not synched to the same time. It is extremely rare to find two geographically separated oscillators to oscillate at the same frequency. This is a big issue in latency measurement of WAN traffic between two geographically separated WAN gateways. The source port of IxNetwork and the receiving port of IxNetwork need to be time-synched to accurately measure traffic latency.

This is the exact remedy provided by the Ixia Metronome Timing System. Metronome relies on GPS time input to enable two geographically separated Metronome devices to provide the same time input to Ixia hardware.

IxNetwork and the Metronome Timing System is the perfect combination for SDWAN validation engineers.